merrill



July s, 192s.y R,... 16,379 A.Aa. MERRILL A Imaan lum 'APPARATUS mi iuumm nnss origin; Fried -nov. 7. 192i Reinued July 6, 1926.

UNITED STATES PATENT oFFlcE.

ALLAN B. MERRILL, OF AKRON, OHIO, ASSIGNOR T THE B. F. GOODRICH COIPANY,

OF NEW-YORK, N. Y., A CORPORATION OF NEW YORK.

METHOD AND APPARATUS FOB MAKING TIRES.

Original llo. 1,435,970, dated November 21, 1922, Serial No. 513,819, illed November '1, 1921. Application.

for reissue led December 13, 1923. Serial No. 880,541.

This invention relates to methods and apparatus for making tires, and more particularly to the art of vulcanizing tires wherein the tire is held distended, during vulcaniza'- tion, by an expansible core, commonly called an air-bag or a. water-bag. My object is to increase the life ofthese bags by. delaying the migration of an excess of sulphur into the walls of the bag from the tires being vulcanized, which eventually4 hardens these walls and causes the bag to crack.

The accompanying drawin is a sectional, perspective view of a water ag embodying a referred form of my invention.

ferring to the drawing, 10 designates the bag as a whole, of .which the main body 11 is a. thick-walled, annular tube of vulcanized soft rubber having at its inner periphery a bead-engaging a m of vulcanized rubber reenforced with stri s of fabric 13. The outer surface of the tube 11, except at the reenforced base 12, is'

covered with a layer of rubber initially containing very little or no sulphur, commonly referred to as a non-vulcanizing compound.

plied to the surface of the layer 14 to prevent the latter from sticking to the inner surface of the tire. 15 is a. valve stein such as is used in inner tubes for pneumatic tires u for supplying fluid under pressure to the intorior of the bag.

In uee,'the 'layer 14 absorbs the sulphur emanating from the tire body and prevents it from reaching the main body 11 of the bag and overcuringr the latter. As the outer layer initially contains but a very small quantity of sulphur, if any, it is capable of absorbing such sulphur as is given off to it by the tire bod in a large number of vulcanizing heats efore it becomes overcured. The bag, nevertheless, withstands handlingr and retains its shape by reason ot the vulcanized condition of the thick-Walled bodyportion 11 andthe base 12.

' The bag may be made in any known or .suitable manner, as by first forming the tliiclm'fzilleil lube l1 of: A vnlcaniznble conv pensi on a .straight mandrel, removing it se portion 12 y pigpose of stiffening it, sinceI the degree of fromthe mandrel and applying the valve stem 15 thereto, joining the endsof the tube to form an annulus,.1nilating it, applying the base portion 12 thereto, stretching onto said annulus the non-'curing sheet of gum 14 and stitching the latter in place, sub- 'ecting the entire structure to vulcanizing eat in a mold while subjecting it to internal uid pressure, painting the surface of the molded bag with a. thin rubber cement containing finely-divided mica and permittin said cement to dry. I do not limit mysel ,`however, to this or any other method of constructing the bag, vnor do I wholly limit myself to the use of mica or to the use of cement as a' vehicle for applying a non-adhesive substance.

I may use a' small amount of sulphur, pref- -fiarably less than 2%, in the veneer 14, with or without a filler or an accelerator, for the canization which results therefrom in 'I6 said veneer is comparativelv small'and the veneer is still capable of absorbinga substantial quantity of sulphur and withstanding many successive heats before it becomes overcured.

In practice I find it advisable to apply a new coat of the mixture of mica and cement before each cure, as a safeguard lagainst sticking of the bag to the -tire and to retard to some extent the migration ofsulphur.

When the outer surface of the veneer 14 eventually becomes overcured and Abe ins to crack, a part or all of it may be bu ed o6 an'd replaced by a new layer of the substantially sulphur-face compound, and as the body portion 11 contains little if any more sulphur than it did originally the bag again may be used 4for a large number of cures. This process of renewing the bag is not a part of my invention, but after such renewal, as Well as before, the bag itself embodies my invention. n

My invention is subject to modifications, and is not wholly limited, for example, to making the sulphur less or low-sulphur layer as a part of the bag.

I claim:

1. An expansible core for vulcanizin rubber articles, said core comprising a wal of vulcanized rubber and a surface layer of relatively vnon-vulcanizing material thereon outermostlayer of rubber in said core initially containing lessv than 2% of sulphur.

' 4. An expansible core for vulcanizing rubber articles, said core comprising a Wall of vulcanized rubber and a layer of substantially sulphur-free rubber thereon, said layer constituting the outermost Ilayer of rubber in said core.

5. An expansible core for vulcanizing rubber alticles, said corel comprisinfr a rubber wall initially containing a smaller proportion of sulphur at the work-engaging surface thereof than in a region relatively remote therefrom.

A6. An expansible core for vulcanizing rubber articles, said core comprisin a stretchable wall, a layer of substantially sulphur-free rubber thereon` said layer constituting the outermost layer of rubber in said core, and material associated with said layer adapted to prevent the latter from sticking to the Work.

.7. An expansible core for Avulcanizing rubber articles, said core comprising a stretchable Wall, a layer of substantially sulphat-free rubber thereon, said la er constituting the outermost layer of rub er in said which comprises maintaining 1core, and finely-divided mica upon said ayer.

'8. Apparatus for vulcanizing pneumatic tires comprising an annular tube of vulcanized rubber, a coating of substantially sulphur-free rubber compound thereon, said layer constituting the' outermost layer of rubber in said core, and means for preventing said coating from adhering to the surface of the tire when the latter is vulcanized in Contact with said coating.

9. The method of making a rubber tire an expansible, rubber core distended within the tire during vulcanization thereof While preventing over-vulcanization of said core by the presence of a layer of material adapted substantially to prevent migration of sulphur from the tire to the vulcanized parts of the core underlying said layer.

'vulcanization of said core l0. The method of making a rubber tire casing by the eXpansible-core process which consists in interposing a substantially sulphurless layer of' rubber between the tire casing and the expansible core upon which the casing is vulcanized.

11. The method o'f making a rubber tire which comprises maintaining au expansible rubber core distended within the tiredu'ring vulcanization thereof While preventing overby the presence of a layer of substantially non-vulcanizing rubber adjacent to the vulcanized rubber of said core. Y

In witness whereof I have hereunto set my hand this 10th day of December, 1923.

ALLAN B. -MERRILL. 

